In the production and use of petroleum products such as crude oil, some oil may become contaminated with solid and liquid contaminants such as sediments and water. In general, excessive levels of any contaminants in a petroleum product yield a final product that is non-usable. Moreover, the contaminated petroleum product may be difficult to dispose of in an environmentally safe manner.
Sediment and water are the primary unwanted by-products generated in the production of crude oil. All petroleum products contain some sediments and water with different ratios of oil, water and solids in various states of emulsification. In all cases, excessive levels of sediment and water yield a product that is unsellable, non-usable and non-disposable.
In order to utilize this otherwise dormant oil/water emulsion, the level of sediments and water must be reduced to acceptable levels. Conventional prior art processes require some form of chemical treatment to break the emulsion, followed by gravity separation. These processes are generally so expensive that the petroleum product released from the emulsion is often worth less than the cost of treating the emulsion.
The present invention is directed to a novel centrifuge apparatus and method especially adapted for mechanically separating contaminants such as sediment and water from petroleum products. It has particular application in oil field production operations where large volumes of contaminated crude oil can be treated to produce a marketable petroleum product. The apparatus and method of the invention also has application in the refinement and disposal of various oil/water emulsions such as waste oil from manufacturing or transportation operations, heavy grade coring oils, various blends of slop oil and water flood oil skim.
The apparatus of the invention includes a three-stage decanting centrifuge that is especially adapted to separating water and solid contaminants from oil. In the past, three stage centrifuges have been utilized to process different oil based emulsions. In the production of olive oil for example, three stage centrifuges are utilized to separate oil, water, and solid components of the processed olives. Such decanting centrifuges are well known in the art.
In general, however, these types of prior art three stage centrifuges are not suitable for processing heavy emulsions such as those occurring in crude oil production. Additionally, these prior art centrifuges are not suited to the environmental conditions (i.e. temperature climate) that may be encountered in oil field operations, nor the wide range of physical characteristics (i.e. viscosity, water content, solids levels, solids type) of different emulsions to be processed. For these reasons such contaminated oil has been mostly processed by chemical treatment and settling of the contaminants.
Moreover, there is a need for a method of separating contaminants from petroleum products so that these contaminants can be disposed of in an environmentally safe manner. Waste oil from oil spills, manufacturing operations, service stations, and oil refineries for instance, are very difficult to dispose of in an environmentally safe manner.
The present invention is directed to a three stage centrifuge adapted to overcome the limitations of prior art centrifuges and to provide a method suitable for removing contaminants from petroleum products so that the petroleum product may be used and the contaminants may be safely disposed.